Concrete is one of the most used construction material worldwide as it is strong and relatively cheap. Current design for durability is through prescriptive guidance and includes factors such as the disposition of reinforcement to control cracking and crack widths, thickness of concrete cover to reinforcement, quality of concrete and management of water. However, concrete is subjected to a number of degradation processes which hamper the structure to reach its required service life. Problems caused by the corrosion of reinforcement in deteriorating concrete structures are widely encountered across Europe and are recognized as a major limitation upon the durability of many existing structures. The primary reason for premature corrosion is crack formation in the concrete cover. Larger cracks as well as a network of finer cracks allow water, oxygen, chloride, and other aggressive corroding substances to penetrate the concrete matrix to reach the reinforcement. Other forms of deterioration due to processes such as frost action and alkali-silica reaction are less widespread in their occurrence, but no less significant in their effects. Accordingly, to anticipate durability problems during the lifetime of a structure, costly measures of maintenance and repair have to be undertaken.
U.S. Pat. No. 4,536,417, for instance, describes a method for repairing and restoring a deteriorated cement-containing inorganic material such as reinforced concrete by applying a solution of a water-soluble silicate compound to its surface to have it impregnated with said solution, and then top coating said material with cement paste or/and mortar. Further, US2005120660 describes a plastic micro packer for repairing cracks of structure and a method for repairing middle or low pressure cracks using the plastic micro packer. The micro packer is connected to a hole formed in a crack to inject a repairing solution into the crack of a concrete structure, and includes a hollow rubber sleeve having a screw portion formed on the inner surface thereof, a hollow packer body having a screw coupling portion screwed with the screw portion and a nozzle portion connected to a repairing solution injector, a cove, and member connected to the nozzle portion to prevent leakage of repairing solution. The screw portion of the rubber sleeve has a wide top and a narrow bottom, and thereby, is closely contacted to the hole while the lower portion of the screw portion is expanded in a radial direction when the screw coupling portion is screwed with the screw portion. A flange portion is formed at the front end of the rubber sleeve to prevent excessive induction of the rubber sleeve into the hole.
V. Wiktor et al, Concrete Repair, Rehabilitation and Retro fitting III, proceedings of the 3rd international conference on concrete Repair, Rehabilitation and Retro fitting III, ICRRR 2012, 2012, p. 955-960, describes about the development of a liquid bio-based repair system for aged concrete structures.
H. Jonkers et al, Crack repair by concrete-immobilized bacteria, Proceedings of the First International Conference on Self Healing Materials 18-20, Apr. 2007, Noordwijk aan Zee, The Netherlands, Springer, p. 1-7, describes about crack repair by concrete-immobilized bacteria and investigates self-healing potential.